I had to replace the engine in my 98 Dakota ( 3.9L). Since I got it back it runs great til it gets warm, then begins bucking and tries to cut out when I accelerate. If I down shift and get the rpm's high enough it'll run fine til I shift up and the rpm's get low enough. Once it starts to do this it will also stall at idle but starts right up again. Any idea what the problem is? Thanks for any advice. djm

 

check your crank and cam sensor. I have a problem with my crank one it would run okay at lower RPM's than once on the highway it would randomly sort of shut off. I would check all your plugs, wires, cap/rotor.

Check your oil, and it may have been sitting around long enough for you to have bad gas, which might cause this, also water in the tank. But once it's warm I am not sure why that would be.

Did you break it in properly? Or it this still trying to break it in?

 

Sorry, should have mentioned it was a used engine with about 65,000 miles on it when it was installed. Also the prob.started becoming more common. It stopped acting up for a month or two now it's back again?!?

 

hmmm, check your air filter, tps, iac ect... all the sensors on the TB. I would guess IAC if anything. Check all your vacuums. Next check your plugs, they maybe be original, if they are they be almost done and once it gets warm they have little to no spark? Does it seem like a spark hesitation or a gas one? does it feel like a cyl with no gas or no spark? Could even be coil. It sounds like something heat sensitive. You can try also check compression too but with that kind of millage and it runs okay cold, it may not be that but might be a good thing to check. I would do the tune up though on electrical,
Plugs, cap, rotor, wires. Check the coil out, a good way to check would be get a timing light and see if it is on almost all the time at idle when warm.

Check your alternator.

 

Thanks, Sounds like I have some checking to do

 

last time this happened to me it was just the coil. i had the accel aftermarket (crap) coil. just fwi

 

could be a clogged cat maybe?